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{{Short description|Tubular vessels that are involved in the transport of lymph and lymphocytes}}
{{More citations needed|date=April 2010}}
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| Name = Lymphatic vessel
| Latin = vas lymphaticum
| Image = Illu lymph capillary.
| Caption = [[Lymph capillaries]] in the tissue spaces
| Image2 = Gray599.png
| Caption2 = The [[thoracic duct]] and [[right lymphatic duct
}}
[[File:3D Medical Animation of Afferent Vessel.jpg|alt=A still image from a 3D medical animation showing afferent vessels|thumb|263x263px|A still image from a 3D medical animation showing afferent vessels]]
The '''lymphatic vessels''' (or '''lymph vessels''' or '''lymphatics''') are thin-walled vessels (tubes), structured like [[blood vessel]]s, that carry [[lymph]]. As part of the [[lymphatic system]], lymph vessels are complementary to the [[cardiovascular system]]. Lymph vessels are lined by [[endothelium|endothelial cells]], and have a thin layer of [[smooth muscle]], and [[adventitia]] that binds the lymph vessels to the surrounding tissue. Lymph vessels are devoted to the [[propulsion]] of the lymph from the [[lymph capillaries]], which are mainly concerned with the absorption of [[interstitial fluid]] from the tissues. Lymph capillaries are slightly
The vessels that bring lymph away from the tissues and towards the lymph nodes can be classified as [[afferent lymphatic vessels|afferent vessels]]. These afferent vessels then drain into the subcapsular sinus.<ref>{{cite web |title=19.2B: Distribution of Lymphatic Vessels |url=https://med.libretexts.org/Bookshelves/Anatomy_and_Physiology/Book%3A_Anatomy_and_Physiology_(Boundless)/19%3A_Lymphatic_System/19.2%3A_Lymphatic_Vessels/19.2B%3A_Distribution_of_Lymphatic_Vessels |website=Medicine LibreTexts |access-date=28 November 2021 |language=en |date=22 July 2018}}</ref>
The [[efferent lymph vessel|efferent vessels]] that bring lymph from the lymphatic organs to the nodes bringing the lymph to the right lymphatic duct or the thoracic duct, the largest lymph vessel in the body. These vessels drain into the right and left [[subclavian veins]], respectively. There are far more afferent vessels bringing in lymph than efferent vessels taking it out to allow for lymphocytes and macrophages to fulfill their immune support functions. The lymphatic vessels contain valves.
== Structure ==
<!--There is a lot of ambiguity in terminology regarding which vessels are lymph and which is a capillary. Also which have valves, smooth muzcles, etc. I'll alter the text when the confusion clears up--[[User:KC Panchal]]-->
The general structure of lymphatics is based on that of [[Blood vessel#Anatomy|blood vessel]]s. There is an inner lining of single flattened epithelial cells (simple squamous epithelium) composed of a type of [[epithelium]] that is called the [[endothelium]], and the cells are called ''endothelial cells''. This layer functions to mechanically transport fluid and since the [[basement membrane]] on which it rests is discontinuous; it leaks easily.<ref name=pepper>{{cite journal | vauthors = Pepper MS, Skobe M | title = Lymphatic endothelium: morphological, molecular and functional properties | journal = The Journal of Cell Biology | volume = 163 | issue = 2 | pages = 209–13 | date = October 2003 | pmid = 14581448 | pmc = 2173536 | doi = 10.1083/jcb.200308082 }}</ref> The next layer is that of [[smooth muscle]]s that are arranged in a circular fashion around the endothelium, which by shortening (contracting) or relaxing alter the diameter (caliber) of the [[lumen (anatomy)|lumen]]. The outermost layer is the [[adventitia]]
<!--The text on the whole needs reorganization. Right now, am trying to add as much info as possible, which can later be easily organized into appropriate sections. So, there can be some info that is "overlapping"--[[User:KC Panchal]]-->
The lymphatic conducting system broadly consists of two types of
Unlike the cardiovascular system, the lymphatic system is not closed and has no central pump. Lymph movement occurs despite low pressure due to [[peristalsis]] (propulsion of the lymph due to alternate contraction and relaxation of [[smooth muscle]]), valves, and compression during contraction of adjacent skeletal muscle and [[arterial]] [[pulse|pulsation]].<ref name=Shayan2006>{{cite journal | vauthors = Shayan R, Achen MG, Stacker SA | title = Lymphatic vessels in cancer metastasis: bridging the gaps | journal = Carcinogenesis | volume = 27 | issue = 9 | pages = 1729–38 | date = September 2006 | pmid = 16597644 | doi = 10.1093/carcin/bgl031 | doi-access = free }}</ref>
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=== Lymph capillaries ===
The lymphatic circulation begins <!--at the skin--> with blind ending (closed at one end) highly permeable superficial lymph capillaries, formed by endothelial cells with button-like junctions between them that allow fluid to pass through them when the interstitial pressure is sufficiently high.<ref name=baluk>{{cite journal | vauthors = Baluk P, Fuxe J, Hashizume H, Romano T, Lashnits E, Butz S, Vestweber D, Corada M, Molendini C, Dejana E, McDonald DM | display-authors = 6 | title = Functionally specialized junctions between endothelial cells of lymphatic vessels | journal = The Journal of Experimental Medicine | volume = 204 | issue = 10 | pages = 2349–62 | date = October 2007 | pmid = 17846148 | pmc = 2118470 | doi = 10.1084/jem.20062596 }}</ref> These button-like junctions consist of [[Fibrous protein|protein filaments]] like [[CD31|platelet endothelial cell adhesion molecule-1]], or PECAM-1. <!--When the interstitial fluid volume increases the fenestrae are stretched allowing more fluid to enter the
Rhythmic contraction of the vessel walls through movements may also help draw fluid into the smallest lymphatic vessels, [[capillary|capillaries]]. <!--Tight clothing can restrict this, thus reducing the removal of wastes and allowing them to accumulate: This is somewhat out of context--[[User:KC Panchal]]--> If tissue fluid builds up the tissue will swell; this is called [[edema]]. As the circular path through the body's system continues, the fluid is then transported to progressively larger lymphatic vessels culminating in the [[right lymphatic duct]] (for lymph from the right upper body) and the [[thoracic duct]] (for the rest of the body); both ducts ''drain'' into the circulatory system at the right and left [[subclavian vein]]s. The system collaborates with white blood cells in lymph nodes to protect the body from being infected by cancer cells, fungi, viruses or bacteria. This is known as a secondary circulatory system.
===Lymph vessels===
The lymph capillaries drain
== Function ==
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The '''afferent lymph vessels''' enter at all parts of the periphery of the [[lymph node]], and after branching and forming a dense plexus in the substance of the capsule, open into the ''lymph sinuses'' of the [[Cortex (anatomy)|cortical]] part. It carries unfiltered lymph into the node. In doing this they lose all their coats except their [[endothelial]] lining, which is continuous with a layer of similar cells lining the lymph paths.
Afferent lymphatic vessels are only found in
===Efferent vessels===
The '''efferent lymphatic vessel''' commences from the [[Subcapsular sinus|lymph sinuses]] of the [[medulla of lymph node|medullary]] portion of the
Efferent lymphatic vessels are also found in association with the thymus and [[spleen]]. This is in contrast to
==Clinical significance==
[[Lymphedema]] is the swelling of tissues due to insufficient fluid drainage by the lymphatic vessels. It can be the result from absent, underdeveloped or dysfunctional lymphatic vessels. In hereditary (or primary) lymphedema, the lymphatic vessels are absent, underdeveloped or dysfunctional due to genetic causes. In acquired (or secondary) lymphedema, the lymphatic vessels are damaged by injury or infection.<ref name=pmid22064427>{{cite journal | vauthors = Alitalo K | title = The lymphatic vasculature in disease | journal = Nature Medicine | volume = 17 | issue = 11 | pages = 1371–80 | date = November 2011 | pmid = 22064427 | doi = 10.1038/nm.2545 | s2cid = 5899689 }}</ref><ref name=issn>{{Cite journal| volume = 17| issue = 2| pages = 96–104| vauthors = Krebs R, Jeltsch M | title = The lymphangiogenic growth factors VEGF-C and VEGF-D. Part 2: The role of VEGF-C and VEGF-D in lymphatic system diseases | journal = Lymphologie in Forschung und Praxis| date = 2013 | url = https://www.researchgate.net/publication/275031534}}</ref> [[Lymphangiomatosis]] is a disease involving multiple cysts or lesions formed from lymphatic vessels.
== See also ==▼
*[[Meningeal lymphatic vessels]]▼
==Additional images==
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File:Gray1093.png | Section across portal canal of pig. X 250.
</gallery>
▲== See also ==
* [[Lacteal]]
▲* [[Meningeal lymphatic vessels]]
== References ==
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== External links ==
* {{MeshName|Lymphatic+Vessels}}
*
{{System and organs}}
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